1. Field of the Invention
The present invention relates to methods for performing radiosurgery on a patient using microbeam radiation.
2. Description of the Related Art
A radiosurgery method which employs sub-millimeter beams of X-rays, termed microbeams, was patented by Slatkin et al. nearly two decades ago (see U.S. Pat. No. 5,339,347, the disclosure of which is incorporated herein by reference). Subsequent scientific studies of the effects of microbeam radiation have further illuminated Slatkin's work, showing that while the tissue cells in the direct path of a microbeam are destroyed, the region of destruction is sufficiently small in width that the adjacent undamaged tissue is capable of healing the damaged region (see Dilmanian et al., Experimental Hematology, Vol. 35, 2007, pp. 69-77, the disclosure of which is incorporated herein by reference). This feature of microbeam radiation, combined with proper targeting technique, promises a means to destroy diseased tissue without damaging the functionality of the surrounding normal healthy tissue.
The most successful prior art targeting technique is termed multidirectional interlaced microbeam radiation therapy (MIMRT). This technique was patented by Dilmanian et al. (see U.S. Pat. No. 7,194,063 B2, the disclosure of which is incorporated herein by reference). MIMRT is comprised of cross firing from several directions such that the diseased tissue receives dosage in a broad beam pattern while surrounding healthy tissue receives dosage in a segmented beam pattern.
As an example, referring to FIG. 1A, a body of diseased tissue 100 is targeted by three linear arrays of planar microbeams 120, 122, and 124. The direction of motion vectors for these arrays, 140, 142, and 144, respectively, are located in the same plane, XY for the coordinate system shown, and are separated in angle by 120 degrees.
Referring to FIG. 1B, each microbeam array is comprised of planes of radiation with width 180, height 182, and pitch 184. The pitch 184, in this example, is equal to three times the width 180. The height 182 is sufficiently large to span the breadth of the body of diseased tissue.
Referring again to FIG. 1A, the array 122 is displaced by one beam width 180 in the Z direction relative to the array 120. The array 124 is displaced by two beam widths 180 in the Z direction relative to the array 120.
Referring to FIG. 1C, the intersection of arrays 120, 122, and 124 at the targeted body of diseased tissue 100 is shown. The arrays 120, 122, and 124 are interlaced.
Referring to FIG. 1D, a cross section through the diseased tissue 100 is shown. Because the microbeam arrays 120, 122, and 124 are interlaced at the target body 100, the entire volume of the target body 100 is exposed to radiation. Normal tissue outside the target body 100, however, is exposed only to the segmented radiation pattern of the individual arrays. By this scheme, the diseased tissue 100 is destroyed while the functionality of the surrounding normal tissue is spared.
A serious difficulty associated with MIMRT is patient motion. The microbeam arrays 120, 122, and 124 of FIG. 1A are delivered sequentially in time. If the target body 100 moves during the time between deliveries of the respective microbeam arrays, the interlacing of damaged regions in the target body 100 does not properly occur and a broad beam damage pattern is not achieved. As such, the diseased tissue 100 is not completely destroyed. Patient motion on the order of a microbeam width compromises the effectiveness of MIMRT. Patient motion larger than this is guaranteed in practice. As an example, for a target body of diseased tissue located in the lung, MIMRT is completely ineffective.